1. Field of the Invention
The present invention relates to a probe structure used for an electric test in a process of producing a semiconductor device, and more particularly to a construction of a probe structure preferable for testing a great area within a wafer to be tested in one lot, that is, a lot of chips.
2. Prior Art
In the process of manufacturing the semiconductor device, there exists a water testing step of testing a basic electric characteristic by bringing a probe into contact with each of a predetermined pads, which is applied to a wafer forming a lot of LSIs. In this testing step, a probe structure in which a lot of probes are arranged so as to be aligned with a layout of the respective pads of the wafer to be tested is used as a jig. This jig is generally called as a probe card.
The probe card has been conventionally structured such that a narrow needle, for example, made of tungsten (W) or the like is employed as each of the probes, and a lot of narrow needles are bonded and fixed to a substrate. However, this structure has a limit in a number of the probes to be formed. Then, for the purpose of forming more probes, there has been employed a method of forming a lot of conductive projections in a certain main base material in one lot in accordance with a plating, an etching, a whisker growth or the like so as to make them probes. Among them, a case that the main base material is an organic thin membrane having a low elasticity such as a polyimide or the like is particularly referred to as a membrane method. The membrane method is, for example, disclosed in Japanese Patent Unexamined Publication Nos. 9-5355 and 11-160356 and the like. Further, there is a case that the main base material is a high elastic material such as a silicon (Si), a glass or the like. This method is, for example, disclosed in Japanese Patent Unexamined Publication Nos. 8-148533 and 10-123174 and the like.
In this case, in the method of forming a lot of projections in the certain main base material in one 20 lot so as to make them probes, in order to electrically and mechanically connect the probes to the substrate, it is necessary to provide a secondary electrode conducting with each of the predetermined probes within the main base material and connect the secondary electrode to an electrode in a substrate side. A method of forming the secondary electrode can be largely classified into the following two methods.
(1) A method of forming on the same surface as a probe forming surface in a main base material.
It can be said that among the prior arts mentioned above, Japanese Patent Unexamined Publication Nos. 9-5355 and 10-123174 belong to this method. In this case, as well as the secondary electrode is bonded to the substrate, a member having a corresponding rigidity is bonded to an opposing surface to the probe forming surface in the main base material as occasion demands, whereby a flatness and a strength of the main base material are secured.
(2) A method of forming on an opposing surface to a probe forming surface in a main base material.
It can be said that among the prior arts mentioned above, Japanese Patent Unexamined Publication Nos. 8-148533 and 11-160356 belong to this method. In the former, each of the secondary electrodes is connected to the substrate by a wire material and in the latter, a connection is performed by a localized anisotropic conductive rubber.
There has been mentioned above the electrical connection method between the main base material and the substrate in the method of forming a lot of projections in the certain main base material in one lot so as to make them probes. A description will be given below of problems of these methods.
(1) A method of forming a secondary electrode on the same surface as a probe forming surface in a main base material.
In accordance with this method, each of the secondary electrodes should be generally formed at a portion closer to an outer periphery of the main base material than a group of probes. As a result, an outer size of the main base material is increased. Further, in the case of forming a lot of probes, since the probes positioned near a center of the group of probes should be wired to the secondary electrode with passing through intervals among peripheral probes, it is hard to secure a sufficient width for wiring and a length of the wire is increased, so that a resistance of the wire is increased.
(2) A method of forming a secondary electrode on an opposing surface to a probe forming surface in a main base material and connecting the secondary electrode to a substrate by a wire material.
In accordance with this method, since it is hard to mechanically reinforce the main base material, for example, in the case of the membrane method, the main base material is bent due to a load when bringing the probe structure into contact with the wafer to be tested, so that it is impossible to bring each of the probes into contact with the wafer at a uniform load. Further, for example, in the case that the main base material is a silicon or a glass, an excessive stress is generated in the main base material, and the main base material is broken in the worst case.
(3) A method of forming a secondary electrode on an opposing surface to a probe forming surface in a main base material and connecting the secondary electrode to a substrate by an anisotropic conductive rubber.
This method is premised on preparing a layout of electrodes in the substrate side coinciding with a layout of the secondary electrodes in the main base material. However, in general, since a pitch at which the electrodes in the substrate side can be formed is larger than that of the main base material, the electrodes in the substrate side cannot be arranged when it is intended to ideally reduce the pitch of the electrodes in the main base material side. Otherwise, when it is intended to set the pitch so as to correspond to the pitch in the substrate side, the area of forming the secondary electrodes in the main base material side becomes wide, so that it is hard to arrange a lot of probes.
Further, in accordance with this method, since it is necessary to always make the number of the secondary electrodes of the main base material equal to the number of the electrodes in the substrate side, the wire in the substrate side becomes complex in the case of forming a lot of probes, so that a cost of the substrate is increased.